mae 656 - 05-d4
DESCRIPTION
shell laminateTRANSCRIPT
MAE 656 - Advanced Computer Aided Design
05. Shells and Membranes – Doc 04
Shell Laminates
Introduction
Shell structures can be made of just one material or can combine several materials along its thickness.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Introduction
Ansys Workbench (in its version 13) is only prepared to work with a single material shell. This is a big drawback as many shells are made of laminate materials.
Therefore, if we want to define a laminate, we have to insert APLD commands in the Mechanical module.
We will have to interact on the Geometry and on the Static Structural sections.
Note: Although we will only use APLD commands to define laminate elements, these can be used for many other applications, being possible to customize Ansys Workbench as much as wanted.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Definition of the Laminate
In the mechanical module, in the geometry section, are displayed all surface elements that have been defined to simulate the structural component.
It is possible to insert command lines under each one of them. In these command lines we will define the laminate.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Definition of the Laminate
The laminate definition is divided in three blocks:
• Definition of the shell properties
• Definition of the materials included in the laminate
• Definition of the laminate layup
The first line that has to be added in the command file is:
/prep7
This line calls the preprocessor
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Shell Properties
The shell properties are defined as follows:
et, matid, 181 !Specifies the element type, shell 181
keyopt,matid,1,0 !Bending and membrane stiffness (default)
keyopt,matid,3,2 !Use full integration
keyopt,matid,8,1 !Store data of all layers
A detailed definition of all these options can be found in ANSYS manual, in sections:
(// Command Reference // VI. E Commands // ET)(// Element Reference // I. Element Library // SHELL181)
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Material Properties
The first thing that is recommended to do when defining the material properties is to erase all data that may be generated in previous steps:
mpdel, all, 11 !Delete all assigned prop. for material 11
tbdel, all, 11 !Delete all previously assigned tabular data
In this case, the material defined is number eleven. It is recommended to use materials with high numeration to avoid writing the data over materials previously assigned in the Engineering Data section.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Material PropertiesAfterwards we will define all material props:
MP, EX, 11, 139.80e3MP, EY, 11, 10.93e3MP, EZ, 11, 10.93e3MP, GXY, 11, 3.92e3MP, GYZ, 11, 3.92e3MP, GXZ, 11, 3.92e3MP, PRXY, 11, 0.28MP, PRYZ, 11, 0.28MP, PRXZ, 11, 0.28
A detailed description of the different properties that can be defined is found in:
(// Command Reference // XIV. M Commands // MP)
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Section Definition
First we have to give a number to the section and say the type of section that will be defined:
Msect, 1, shell
Afterwards we have to provide some data of the section. In particular, we are interested in defining the staking sequence. This is, the thickness of the lamina, the material and its orientation:
secdata, 0.26, 11, 30 !Define thickness, material & orientation for layer i
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Section Definition
We can also define the position of the laminate relative to the shell geometry:
secoffset, MID!Define thickness location (TOP - MID - BOT)
As happened with the other parameters defined, more information can be found in Ansys help, which can be found in:
(// Command Reference // XX. S Commands // SECDATA)(// Command Reference // XX. S Commands // SECOFFSET)
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Some Notes• The materials defined in a command file (for a particular
shell part) can be used in other command files, without having to redefine them.
• Material properties are defined in the local shell direction. It is recommended to define the orientation axis of the shell in order to have the material correctly oriented.
• All commands described are basic APDL commands. A better description on how to define composite materials using ANSYS APDL can be found in: E. Barbero Finite Element Analysis of Composite Materials (Composite Materials: Design and Analysis). CRC Press. ISBN: 978-1420054330
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Static Structural
After defining the boundary conditions, we have to include an APDL command in the Static Structural section, in order to be sure that Ansys uses the shell section defined.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Static Structural
The lines to be included are the following:
fini !Exit current Module
/prep7 !Call the preprocessor
etcon,off !Disable ANSYS from changin any KEYOPTS
fini !Exit the preprocessor
/solu !Call the Solve Module
It is important to include this command file as the last think defined in the Static Structural region because its last line sends the developed model to the solver. If some boundary conditions are defined after the command line, they may be not considered.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example
Define a rectangular shell structure with dimensions:
Note: All measures are in millimeters.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example
The boundary conditions applied are:
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example
Solve three different laminates to study the interaction between the different deformation modes.
The composites that have to be studied are:
(02, 02, 902)(302, 02, 302)(302, 02, -302)
The middle layers, written in green, are made of material 12. The rest of the layers are made of material 11.
Each layer has a thickness of 0.26mm
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example
The materials defined are:
!Material 11 - Def. of mechanical properties mat 11MP, EX, 11, 139.80e3MP, EY, 11, 10.93e3MP, EZ, 11, 10.93e3MP, GXY, 11, 3.92e3MP, GYZ, 11, 3.92e3MP, GXZ, 11, 3.92e3MP, PRXY, 11, 0.28MP, PRYZ, 11, 0.28MP, PRXZ, 11, 0.28
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example
The materials defined are:
!Material 12 - Def. of mechanical properties mat 12MP, EX, 12, 5.00e3MP, EY, 12, 5.00e3MP, EZ, 12, 5.00e3MP, GXY, 12, 2.08e3MP, GYZ, 12, 2.08e3MP, GXZ, 12, 2.08e3MP, PRXY, 12, 0.20MP, PRYZ, 12, 0.20MP, PRXZ, 12, 0.20
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example (2)
Reproduce the ply drop-off test using shell elements.
In this case we will have to modify the geometry to divide the shell in two different regions. Each one with a different number of layers.
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
3 layers
6 layers
Numerical Example (2)
The boundary conditions are:
With an imposed displacement of 0.5mm
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04
Numerical Example (2)
All layers are oriented in the direction of Xglobal and the material considered is mat 11 previously defined.
The deformation obtained with the solid model for this same problem is:
MAE 656 – cba Dr. Xavier Martinez, 2012 05. Shells and Membranes – Doc 04